Abstract As mineral exploration moves into regions dominated by transported cover, conventional techniques (e.g., lag gravel) may not be applicable and thus, increasingly, there is a need for new, innovative approaches. To develop these approaches, potential mechanisms that transfer metals from buried mineral deposits through cover to the surface need to be identified. This paper presents an overview of some of the experimental and field trials conducted in Australia as part of an industry-supported three-year CSIRO/AMIRA project. The objective was to define vadose zone processes that might form elemental anomalies at surface over buried deposits in semiarid and arid terrains, and to compare methods that detect these anomalies. Studies were conducted at seven sites representing orogenic Au, volcanogenic massive sulfide (VMS; Cu-Zn-Ag), and magmatic Ni mineralization with transported cover ranging in thickness from 2 to 30 m. Three vertical metal migration mechanisms are important in vadose environments: (1) biological, (2) gaseous, and (3) capillary. An integrated approach, combining different mechanisms with the nature and evolution of transported regolith and climatic settings, was considered to obtain the best prediction of metal transfer. Upward element transfer by vegetation (Acacia aneura and Eucalyptus spp.) occurs in areas of transported cover up to 30 m thick, but not in environments which lack supergene enrichment and have hypersaline acid groundwater. Microbial populations are different in soil over mineral deposits than in those from background sites. Metals, detected by gas collectors, are transferred to surface as gases. Soil pit experiments show that strong geochemical anomalies can form rapidly (over 7 months) through 2 m of transported cover, and assist in understanding the genesis of natural geochemical anomalies. Seasonal variations suggest that migration of elements from source to surface may vary in time and intensity. Anomaly formation in the pit experiments is an episodic process largely driven by capillarity, in which batches of metals in water-soluble form are translocated. Soil-forming processes may form false anomalies and the data need to be interpreted with care.

Abstract This chapter describes the metallic ore deposits of Chile, their mineralized host rocks and the processes involved in ore formation, and provides a brief overview of the mining history of this Andean copper-rich country. The ore deposits are ordered according to their respective economic importance. Thus, after mining history and a general introduction, Chilean porphyry copper–molybdenum deposits are described first, with subsequent sections dealing with epithermal precious metals, iron oxide copper–gold and iron oxide–apatite deposits, stratabound copper–(silver) ores, precious metal veins, sedimentary-hosted gold and porphyry gold deposits, skarn rock ores and, finally, an overview of metallogenic evolution. About 40% of the known copper resources of the world occur in Chile, with the native populations using the red metal at least since 500 BC. Bracelets, earrings and weapons that have been found in archaeological sites in northern Chile were made of either native copper or copper-rich minerals that were melted in small quantities and subsequently hammered. Copper production during Spanish colonial times (1541–1810) amounted to some 80 000–85 000 tons, with high-grade oxidized copper minerals being exploited and melted with charcoal. Despite this mining activity, however, Spaniards regarded copper as ‘plebeian metal’ because of its relatively low value, and it was used mostly as ballast for ships returning to Spain, rather than for technological or industrial purposes. The colonial Spaniards were much more interested in gold and silver, and mining activities were consequently mostly orientated towards precious metals. Prior to Spanish conquest the Incas dominated northern Chile and had already exploited